Magnetic depth indexing means



May 26, 1970 s. T. BOOP MAGNETIC DEPTH mnsxme MEANS Filed Aug. 5, 1967FIG. I

INVENTOR. GENE II BOOP MARCUS L. BATES United States Patent 3,513,912MAGNETIC DEPTH INDEXING MEANS Gene T. Boop, 3509 Clearmont, Odessa, Tex.79760 Filed Aug. 3, 1967, Ser. No. 658,215 Int. Cl. E21b 43/119; H01f7/02 US. Cl. 166--65 3 Claims ABSTRACT OF THE DISCLOSURE A magneticdevice associated with a casing, liner, or tubing of an oil well whichenables a magnetic sensing device, such as a collar locator, to positionvarious tools with exactness with respect to a predetermined locationdownhole of the well head. The magnetic device may consist of a numberof magnets arranged in an internal annular groove in the casing, liner,or tubing, and spaced apart by plastic material.

BACKGROUND OF THE INVENTION This invention relates to apparatus forlocating tools and the like at a predetermined distance downhole of aborehole with great exactness by the use of a magnetic sensing devicesuch as a collar locator.

In carrying out drilling operations in order to produce hydrocarbonsfrom formations located deep within the ground, the well, or borehole,is generally drilled to a depth of three hundred to one thousand feet,and a surface casing is then cemented into the borehole. The bit is thenreduced in size, and the middle portion of the hole drilled, with thisoperation being called the salt string, or the middle string. The bit isagain reduced in size and the oil string drilled. The oil string goes tothe bottom of the hole. The borehole is therefore lined with casingwhich may be called the surface casing, the salt string, and the oilstring. The casing is made up of multiple joints of pipe, with a collarthreading the joints together. Sometimes a liner is used, especiallywhere it is desired to plug off the old casing. The liner usually has nocollar but instead is threaded together by employing male and femalethreads at opposite terminal ends of each joint of liner.

A collar locator, a device Which measures changes in mass in terms offlux density, is used to determine the position of the various collarswith respect to a reference SUMMARY It is desirable, in carrying outcertain operations on oil wells, to be able to exactly determine thelocation of various strata associated with the borehole. The use of acollar locator provides a means by which the well may be calibrated withrespect to a location above the borehole. The expedient requires carefulobservations along with intimate knowledge of the location of thevarious collars associated with the bore hole. The present inventionenables one or more collars having magnetic means associated therewithto be included within the bore hole so as to give a point of index farbelow the surface of the earth which accordingly provides the oil welltechnician with a precise means by which the depth being analyzed may bedetermined. For example, it is consoltion.

It is therefore a primaryobject of this invention to provide a boreholewith a magnetic means which enables the exact determination of the depthof the well near a particular strata.

Another object of the present invention is the provision of a casingcollar having magnetic means associated therewith which enables amagnetic collar locator to easily and unmistakably determine thepresence of the magnetic collar.

Another object of the present invention is the provision of a magneticmeans associated with the various tubing, pipe, or casing of a boreholewhich enables indexing of downhole tools and apparatus with respect tothe depth of the Well in an exact and precise manner.

A still further object of the present invention is the provision ofmagnetic means which enables one to sequentially locate the magneticmeans at a predetermined spaced apart interval to enable various zonesof the well to be coded to thereby readily identify the various zones ofthe well.

A still further object of the present invention is the provision ofmagnetic identifying means associated with the various tubing and thelike of an oil well to enable the determination of the exact depth oftools and various apparatus within an oil well.

The above objects are attained in accordance with the present inventionby the provision of a magnetic means located a predetermined distancedownhole in a borehole.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial cross-sectionalview of a portion of an oil well casing showing the depending ends oftwo sections of tubing connected together by a collar, wherein thecollar is made in accordance with the present invention;

FIG. 2 is a fragmentary cross-sectional view of an oil well casingcomprised of two depending ends of a liner and showing the presentinvention operatively associated therewith;

FIG. 3 is an enlarged fragmentary cross-sectional view taken along line3-3 of FIG. 1;

FIG. 4 is a cross-sectional view of a modification of the device seen inFIG. 3;

FIG. 5 is an enlarged fragmentary representation similar to theembodiment of FIG. 4;

FIG. 6 is a view similar to FIG. 5, but showing a modification thereof;

FIG. 7 is an enlarged cross-sectional view of still another modificationof the device seen in FIGS. 1 and 2;

FIG. 8 is a cross-sectional view, similar to FIG. 7, and showing stillanother modification of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a small portion orsection of an oil well casing, as generally illustrated by the arrow atnumeral 10. The casing is comprised of a terminal end portion of tubings12 and 14 which are threadedly connected together in the usual manner bya collar 16. Threads 18 and 20 are spaced apart and an annular groove 22provided in the illustrated manner therebetween. A magnet 24 having anorth and south pole is rigidly afiixed within the groove by epoxycement 26 and 28. While epoxy cement is recited as being desirable, thisterm should be understood to include fiber glass resin and the like.

Looking now to FIG. 2, the casing is comprised of a liner which includesthe depending ends of a tube, pipe, or the like, as indicated bynumerals 30 and 32. The liner includes male and female threads 34. Anannular groove 36 is circumferentially described about the insideperipheral wall portion of the liner, with the groove being spaced apartfrom, adjacent to and clear of the threads. A magnet 38 is securedwithin the groove 36.

Looking now to FIG. 4, there is illustrated a magnet carried by acollar, tubing, piper, or liner 40, with the tubing having an annulargroove 42 circumferentially disposed therein and carrying individualmagnets 44 which are spaced apart and cemented in place by fiber glassresin 46.

Looking now to FIG. 5, which is similar in many respects to theembodiment of FIG. 4, there is seen a groove 50 having an upper edgeportion 52 circumferentially disposed about the inside peripheralsurface of an oil well casing or tubing and wherein there is suitablymounted a multiplicity of magnets 54 which are vertically aligned inparallel relationship with respect to each other and spaced apartthereby leaving spaces 56 therebetween. The magnets 54 may be individualmetallic magnets or may be individual rectangular plastic inserts.

The plastic insert is similar to the insert 44 of FIG. 4 when viewed incross-section, and is of a thickness which enables the inside peripheralwall surface thereof to coincide with, or to be continuous with, theinside diameter of the pipe. It is further preferred to make the lengthof the insert several times longer than the width thereof.

In FIG. 6 there is seen an annular groove 60, similar to the groove 22or 36 of FIGS. 1 and 2 respectively, and wherein the groove 60 has alower marginal edge portion 62 with two aligned rows of small pin likemagnets, 64 and 66, disposed therein, leaving an annular groove 68therebetween. In other words, the annular grooves 60 carry twocircumferentially disposed rows of magnets 64 and 66 therein, with eachrow of magnets being spaced apart with the the groove to leave a smallergroove 68 between the adjacent but spaced apart ends of the rows ofmagnets.

As seen in FIG. 7, the wall of a pipe or collar 70 is suitably milled toprovide an annular groove 72 therein which carries a magnet 74 withinthe groove. The depend ing ends of the magnet are spaced apart as seenat 76, thereby leaving a north and south pole as illustrated.

The discontinuous ring 74 may be of any desired width which isconsistent with the groove dimensions so as to enable the ring to bereceived within the groove. The ring has an inside diameter slightlygreater than the inside diameter of the groove so as to enable the ringto be compressed, placed within the groove, whereupon release of thering enables it to expand against the outer peripheral groove wallsurface where it is rigidly held caged by the compressive force exertedbetween the ring and the groove wall. The ring is preferably fabricatedof a magnetic material which is sufiiciently resilient to enable thespring action of the ring to attain this function.

FIG. 8 shows a groove 82 placed in a wall 80 and carrying two magnets 84therein with the magnets being more or less C-shaped and having spacedapart depending end portions as seen at 86 and 88. While the poles arearranged N-N and S--S with respect to each other, they may be reversedwith respect to each other so as to present unlike poles adjacent eachother, although it is preferred to place the poles in the indicatedmanner of FIG. 8.

Looking again to the embodiment of FIGS. 1 through 3, it will now beseen that the magnet 24 can be cut from a strip of magnetic tape (forexample, magnetic tape having the tradename .Magnyl Magnetic Strips;manufactured by Chart-Pak Inc.), with the tape being cut a width andlength equivalent to the width and circumferential length of the groove22. The depth of the groove 22 is preferably slightly deeper than thethickness of the magnetic tape. The magnet is held in place by fiberglass resin which strongly adheres the tape within the groove of thecollar as indicated at 22, while at the same time provides a protectivefilm as indicated at 28.

The magnetic tape can alternatively be cut into strips and placed withinthe groove in the spaced apart manner illustrated by FIG. 4, with theepoxy resin filling the voids 46 therebetween.

Where deemed desirable, magnetized metallic bars may be cemented intothe groove in the illustrated manner of FIG. 5.

In the embodiment of FIG. 6, small magnetic needles 64 are alignedWithin the groove and secured in place by fiber glass resin which ispainted thereon. This expedient provides a double pole magnet whereinlike poles may be arranged at the small groove 68 to thereby provide asharp change in flux at the groove.

In carrying out the present invention, the magnetic means are placedwithin the casing at predetermined levels near oil or gas bearingstrata. It may be desirable, for example, to place a magnetic couplingat various depths, for example each one thousand foot intervals, so asto enable a perforating gun crew to rapidly drop the gun into the holewith no fear of overrunning the gun and hitting the bottom. Furthermore,various depths may be coded, or indexed, by placing a multiplicity ofmagnets at spaced apart intervals, such as for example, a fifteenthousand foot depth may be suitably indexed by a combination of magnets,assuming this level to be near one of the oil bearing strata.

In carrying out the present invention, assuming that an oil bearingstratum at fifteen thousand two hundred feet is to be perforated, andassuming that the zone has been indexed with the magnetic collar atfifteen thousand feet, the perforating gun is run into the hole with amagnetic collar locator attached thereto, and the gun is stabilized atthe fifteen thousand foot level exactly and within a fraction of an inchfrom the magnet associated with the collar. The gun is then loweredexactly two hundred more feet as measured from the top of the wall,whereupon the perforation is then carried out at the precise locationrelative to the oil bearing strata, with an error amounting to less thanone inch.

I claim:

1. In a borehole located in the ground and having tubular memberstherein, such as casing or production tubing, means for indexing oilwell equipment at predetermined depths within the borehole comprising:

means forming an inwardly opening annular groove within one of saidtubular members, said groove adapted to be spaced at a known distancebelow the surface of the ground;

a permanent magnet rigidly afiixed within said groove;

said magnet being comprised of a plastic material and a multiplicity ofindividual elongated magnetic bodies, said magnetic bodies being held inspaced apart relationship by said plastic material, each individual bodyhaving a length greater than its width, with each body being parallel toeach other;

said groove being circumferentially disposed for 360 about the insideperipheral surface of said tubular member, the width of said groovebeing approximately equal to the length of each said body; and

each of said individual bodies being longitudinally disposed within saidgroove with respect to said tubular member.

2. The indexing means of claim 1 wherein said permanent magnet has amajor diameter equal to the major diameter of the groove, and saidpermanent magnet has magnets being superimposed above the other row ofmag- 5 nets to thereby leave a circumferentially disposed annular groovebetween each row of individual magnets.

References Cited UNITED STATES PATENTS 2,147,544 2/1939 Potts 166-662,228,623 1/1941 Ennis 1664 2,350,832 6/1944 Segesman 16666 X 3,106,96010/1963 Doak 166-64 X 3,171,486 3/1965 Ownby 166-65 FOREIGN PATENTS642,353 8/1950 Great Britain.

DAVID H. BROWN, Primary Examiner 0 I. A. CALVERT, Assistant Examiner US.Cl. X.R. 335303

